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Free Energy of Dissolution

The free energy of dissolution (ΔG_dissolution) determines whether a solute will spontaneously dissolve in a solvent. It combines enthalpy (ΔH) and entropy (ΔS) changes in the process.

Key Concepts​

  • Gibbs Free Energy: ΔG = ΔH − TΔS
  • ΔG < 0 → dissolution is spontaneous
  • ΔG > 0 → dissolution is non-spontaneous
  • Temperature (T) affects solubility through the TΔS term

Factors Affecting ΔG_dissolution​

  1. Lattice Energy: Energy required to separate solute ions
  2. Hydration Energy: Energy released when solute ions interact with solvent
  3. Entropy Change: Increase in disorder favors dissolution

Example​

For NaCl(s) → Na⁺(aq) + Cl⁻(aq):

  • Lattice energy is endothermic
  • Hydration energy is exothermic
  • Entropy increases → ΔG_dissolution < 0 → NaCl dissolves spontaneously

Importance​

  • Predicts solubility of salts and compounds
  • Helps in designing solutions in chemical processes
  • Important in pharmaceuticals, materials science, and environmental chemistry

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